Fires and hazards of fire (or associated environmental dangers) associated with industrial tanks for storing liquid petrochemicals and other chemicals are typically addressed using “master stream” fog nozzles (500 gpm or greater nozzles.) These nozzles offer both a straight stream and a fog pattern and are staged on a monitor because of the level of their reaction forces. The nozzle size and capacity of master stream nozzles might run to 10,000 gpm or greater. Such nozzles and monitors are typically staged on or outside of the industrial tank itself.
The industrial tanks for storing liquid petrochemicals and other chemicals are being constructed with ever increasing diameters. Diameters have grown from approximately 50 feet to over 300 feet in the last 25 years. (Storage tank walls are typically 50-60 feet high.) The increase in the size of the tanks is challenging the capacity of traditional master stream fog nozzles, staged a minimally safe distance from the tank and used for over the wall application. Traditional master stream fog nozzles are challenged today to reach the full extent of a tank surface in order cover the tank surface with a foam blanket, even in ideal conditions.
Practical factors that further affect the reach of nozzles include wind, heat and personal safety. Wind limits the staging of nozzles to the generally upwind side of the tank and can adversely affect the landing footprint of the foam. Heat and personnel safety can affect where nozzles can be staged in given circumstances. (Note: the necessity to stage crews closer to large tank fires in order to satisfy the range requirements for the nozzles has resulted in nozzle handles melting off due to heat.)
Master stream “fog” nozzles, as utilized for large industrial tank fires, typically discharge from an annular port surrounded by a sliding sleeve. The annular port is typically created by locating a baffle in the nozzle barrel. The sliding sleeve provides an adjustment of the nozzle discharge from the annular port from a straight stream pattern to a full fog pattern. The full fog pattern discharges significantly laterally to provide associated fire fighters and equipment protection from fire and heat, when or as needed.
The full fog pattern is usually achieved by sliding the sleeve back along the nozzle such that it reinforces, enhances or duplicates the swedge angle of the nozzle barrel downstream from the annular discharge gap. The swedge angle of the nozzle barrel is a beveled angle that helps guide the stream discharging from the annular port in its outer circumference. A swedge angle might provide approximately 40 degrees of latitude from the downstream direction. The straight stream pattern is typically achieved by sliding the sleeve forward in the downstream direction such that the liquid discharged from the annular discharge port through the gap, after being directed initially by the swedge angle of the nozzle barrel, becomes redirected by the sliding sleeve in a direction approximately parallel with the axis of the nozzle and/or the downstream direction.
Tests have shown that a straight stream pattern from an annular discharge port can frequently achieve greater range than a solid bore discharge port. At the least, testing shows that a proper straight stream pattern from a well designed annular port nozzle achieves at least 85% to 90% of the range of the very best solid bore nozzle designs in the industry where those solid bore nozzle designs are optimized for range at the same gpm.
Accord “A Guide to Automatic Nozzles,” 1995, Task Force Tips.
A further benefit of the annular discharge port design (“fog” nozzle design) over the solid bore nozzle design when adjusted for a straight stream pattern is that the fog nozzle discharge lands in (what is referred to in the industry as) a footprint that is tightly defined. A predictable, tightly defined footprint enables the staging of nozzles so that application rate density plus foam run can be confidently relied upon to blanket a tank with foam within a requisite time period. The predictable, tightly defined footprint permits forming dependable strategies for attacks on a tank fire. Solid bore nozzles, on the other hand, although at times capable of being adjusted and designed for greater range for a given gpm, tend to have a “rooster tail” trajectory and discharge, producing a long narrow, more poorly defined landing footprint. Such poorly defined, large landing footprint is less useful in blanketing a tank with foam and less useful in forming dependable strategies for attacks upon a tank fire. The rooster tail trajectory and large landing pattern, further, is more vulnerable to being distorted, by wind, and thus rendered each is less reliable and predictable.
The trend of ever increasing tank diameter sizes, mentioned above, at times is placing increasing demands on the effective range of master stream fog nozzles. Nozzle range limitations, when other possible adverse effects of associated equipment, resources and environment are factored in, can create problems for the fire fighter.
Limitations of equipment, resources and environment affecting a nozzle's range include not only wind but limitations on staging, hose length, monitor design, pump capacity and water and head pressure. Any of these factors can result in the actual reduction of the range achievable by a nozzle in a given situation, a reduction to something below the design range of a nozzle. As a result, enhancing the range of a given size of a master stream fog nozzle is significant and valuable. However, a sacrifice of the predictable, tightly defined landing footprint and the fog capability of the nozzle for emergencies, is not acceptable.
A recent 285 foot tank seal fire in a tank of crude oil emphasized to the instant inventor the criticality of enhancing the range for a given gpm master stream fog nozzle even by 10%. A Daspit tool was developed and had been deployed that would allow for a four inch monitor and an associated 2000 gpm nozzle to be carried up a ladder or stairway of a tank and to be affixed to a tank side wall. From a personnel safety standpoint, the safest place to affix the tool is proximate the landing at the top of the stairway. These landings have railings. A five inch hose, brought up the wall to supply the fighting fluid to the nozzle and monitor, can blow its coupling or become uncoupled. A loose hose represents a substantial danger to personnel. The danger is immeasurably enhanced if, because of nozzle range limitations, fire fighters must utilize the four foot wide, railless gutter along a tank wall in order to stage a nozzle close enough so that the range covers the fire, instead of the landing with a railing. The use of the railless tank gutter was required at the 285 foot tank crude oil seal fire in order to achieve the necessary range. Subsequently, the instant inventor, strongly motivated, developed, by extensive and varied testing, the instant novel structure and design for extending the range of a given gpm master stream fog nozzle, surprisingly, without sacrificing the tight landing footprint characteristic of the traditional annular discharge port and without giving up fog capability.
(Note: increasing monitor size, e.g. from a four inch monitor to a five inch monitor, would decrease pressure loss in the monitor and would also increase a nozzle's range. However, increasing the monitor size to 5 inches tends to render existing monitors essentially non-portable by humans, in regard to carrying a monitor up a tank wall, and might over reach the water supply capability.)
The instant inventor had previously invented a HydroChem and a DualFluid nozzle (see U.S. Pat. Nos. 5,167,285 and 5,312,041) which extended the range for throwing dry chemical or powder or particulate matter or CO2 or other light material toward a fire. (The problem of throwing fire extinguishing powder has been likened to the problem of throwing feathers.) Extending the throw of dry powder and/or other light fluids to close to the range of water was accomplished by throwing the powder or light fluid within the initially hollow cylinder/cone pattern formed by the annular discharge orifice of a master stream fog nozzle, when set in a straight stream pattern.
The instant inventor was also familiar with and involved in the invention of a self-educting nozzle design. The self-educting fog nozzles have an inner straight bore for self-educting foam concentrate and for discharging the concentrate at the annular discharge port. See U.S. Pat. No. 4,640,461.
Although increasing the throw of water (or water/foam concentrate) is not like increasing the throw of a light material like powder, or “feathers,” (e.g. the result sought by the inventor was not to extend the throw of “a light” fluid but rather to extend the throw of the water or foam itself), nonetheless, among his varied testing the instant inventor experimented with modifying a dual fluid and a self educting nozzle design in certain ways. That is, he experimented with throwing a solid stream of water within an annular stream of water, the annular stream being the stream of the normal hollow cylinder/cone of water thrown by a straight-stream adjusted master stream fog nozzle. He then compared throwing a solid bore stream of water with throwing an equivalent amount of water in an annular discharge straight stream pattern, and both with throwing an equivalent amount of water partially in a solid bore stream surrounded by water in an annular discharge straight stream pattern. (What holds for water is expected to hold for water/foam concentrate or foam.)
The surprising results were that throwing an appropriately structured solid stream of water within a hollow cylinder/cone discharge of an appropriately structured annular discharge, adjusted for straight stream pattern, resulted in a range of approximately that of the very best solid bore design alone (the solid bore design which had the longest range,) while retaining the annular stream's tight landing footprint. Thus, for the same gpm, with the new design range could be increased beyond that of throwing an annular stream alone while the tight landing footprint characteristic of the annular discharge, was retained. This proved true for a 50/50 split of the inlet water up to 90/10 split, bore to annular conduit. At a 90/10 bore/annular conduit split, range was increased essentially to the equivalent of the very best solid bore nozzle while the tight landing footprint pattern of the annular discharge port, adjusted for straight stream, was not sacrificed. The safety feature of the full fog option, of course, was retained. (An effective full fog option does not require a fog pattern for 100% of the water.)
The division of inlet water (or fluid) between the annular conduit and the straight bore conduit could be variously adjusted in the nozzle, when desired, by such means, for example, as screwing a baffle in or out and/or by replacing a bore/baffle tip. For most operations a 50/50 split of the water might optimize the combination of range and tight landing footprint. A 90/10 split, however, could be used when range was the highest priority while a fog capability was still important for safety purposes. The desired gpm of the nozzle might affect the choice, also.
Once the invention was made, it clearly also had application to even smaller nozzles, such as from a 95 gpm to a 500 gpm nozzle size. Such lower gpm nozzles may be hand held.
To recap, for a given gpm, the very best range optimized solid bore nozzle design might achieve a 10% to 15% greater range than a range optimized fog nozzle design, adjusted for straight stream. However, a range optimized solid bore nozzle can not demonstrate a reliable tight landing footprint while achieving its optimized range. Surprisingly, testing now shows that a 50/50 to a 90/10 combination (split of water between a solid bore and an annular port respectively) of a solid bore with an annular design, range optimized and adjusted for straight stream, achieves the same or almost the same range as the very best solid bore designs without sacrificing the tight landing footprint characteristic of the annular bore design, and while providing full fog capability. (The ratios reflect the proportion of bore liquid to annular liquid.) The instant inventor speculates that the cylinder/cone discharge pattern of the annular port design where adjusted for straight stream creates a low pressure area within which may help preserve the energy of the solid stream and provide an envelope to preserve the annular bore landing pattern.